1. Field of the Invention
The present invention relates to a side structure of a vehicle. More particularly, the invention pertains to a side structure of a vehicle having a sliding side door for opening and closing a door aperture in a side of the vehicle, the side structure featuring a capability to reduce intrusion of the sliding side door into a passenger compartment in the event of a side impact crash.
2. Description of the Related Art
Japanese Laid-open Utility Model Publication No. 1994-74436 (hereinafter “Suzuki '436 Publication”) introduces two different arrangements for reducing intrusion of a sliding side door into the interior of a vehicle caused by side impact crashes. One of these arrangements (first arrangement), shown as an example of a prior art technique, is such that a downward-extending locking pin is provided on a bottom surface of a side door while an upward-projecting retaining part for receiving the locking pin is mounted on top surface of a side sill. The other arrangement (second arrangement) disclosed in the Publication is such that a hook-shaped engaging member projecting inward in a lateral direction of the vehicle is fixed to a lower end portion of an inner panel of a side door while a hole for receiving the hook-shaped engaging member is formed in a side surface of a side sill.
Suzuki '436 Publication argues that the first arrangement works effectively in a case where the amount of overlap between a lower end portion of the side door and the side sill is small, or if a lower end of the side door is located at about the middle of the height of the side sill. On the other hand, the Publication states that the second arrangement is effective in a case where the amount of overlap between the lower end portion of the side door and the side sill is large, or if the lower end portion of the side door is shaped to cover the side surface of a side sill.
The side sill is a mechanical element exposed to the exterior of the vehicle when the side door is opened. For this reason, the provision of the retaining part or the hole in the side sill shown in Suzuki '436 Publication is not preferable from the viewpoint of external appearance. As illustrated in the drawings appended to the Publication, the side sill is made up of the aforementioned inner panel and an outer panel. The side sill thus structured must have sufficient stiffness to reduce intrusion of the side door into the vehicle interior in side impact crashes. It is therefore essential to carefully study a side sill reinforcement structure if either of the arrangements shown in Suzuki '436 Publication is to be embodied in a side structure of a vehicle. In addition, this approach is likely to result in increases in the number of components and manufacturing cost.